.page{
    width: 1600px;
    border: 2px solid;
    margin: 0 auto;
}

.page1{
    background: lightblue;
}

.page2{
    background: lightgreen;
}

.nav{
    position: fixed;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    background: #008c8c;
    color: #fff;
    padding: 20px;
}

.nav a{
    color: inherit;
    display: block;
    margin: 20px 0;
    text-decoration: none;
    font-size: 2em;
}

.nav a.active{
    color: yellow;
}
